Riello Fan Overrun / Stuck Relay

Boiler fan runs continuously even when there is no demand for heat

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Stuck fan relay on PCB, Faulty flue temperature sensor keeping fan on, Incorrect wiring from external controls

Safety: Continuous fan operation wastes energy and may indicate a control fault.

Check demand indicators: Ensure there is no call for heat or hot water from external controls.
Power cycle: Turn off power for 30 seconds and restore. If the fan starts immediately with no demand, the PCB relay may be stuck.
Sensor check: A technician should test the flue temperature sensor and PCB outputs and replace the faulty component.

Hard 4/5

Main Control PCB

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